1. Technical Field
The present invention relates to a soft magnetic powder, a dust core, and a magnetic device.
2. Related Art
In recent years, mobile devices, such as notebook computers, are markedly reduced in size and weight. Furthermore, notebook computers in recent years have capabilities that are enhanced and equivalent to desktop computers.
For the reduction of size and weight and the enhancement of the capabilities of mobile devices, it is necessary to provide a switching power supply driven at a high frequency. Accordingly, the driving frequency of the switching power supply has now been increased to several hundred kHz, and associated therewith, the driving frequency of the magnetic devices, such as a choke coil and an inductor included in a mobile device, is also necessarily increased.
For example, JP-A-2007-182594 discloses a thin strip formed of an amorphous alloy containing Fe, M (wherein M represents at least one element selected from Ti, V, Zr, Nb, Mo, Hf, Ta and W), Si, B and C, and also discloses a magnetic core produced by laminating the thin strips and punching out the laminated thin strips. The magnetic core is expected to enhance alternating current magnetic characteristics.
However, the magnetic core formed with the thin strips necessarily suffers considerable increase of Joule loss (eddy current loss) due to the eddy current as the driving frequency of the magnetic device is further increased.
For solving these problems, a dust core has been used, which is formed by press molding a mixture of a soft magnetic powder and a binder.
A soft magnetic powder constituted by an amorphous alloy material has a large resistivity, and thus the eddy current loss is suppressed in a magnetic core containing the soft magnetic powder. As a result, the iron loss at a high frequency can be lowered. In particular, an Fe-based amorphous alloy has a large saturation magnetic flux density, and thus is useful as a soft magnetic material for a magnetic device.
However, the Fe-based amorphous alloy has a large magnetostriction and thus has a problem that it generates heat at a particular frequency, and enhancement of the magnetic characteristics (for example, reduction of coercive force and increase of magnetic permeability) is prevented.